1. Field of the Invention
The invention pertains to a new or improved method or process for the production of workpieces that are at least internally profiled in a straight or helical manner and, relative to the workpiece axis, if desired, can also have an outer profile that is straight or helical relative to the workpiece axis.
When profiling is produced on both the inside and outside surfaces, more or less close similarity or far reaching differences between the inner and outer profile can be produced.
The profiling can, if required, also be limited to axially extending areas and/or in circumferentially extending areas. A typical example of such a profile could be a gear.
2. Discussion of the Background of the Invention and Material Information
For the production of quality precision profiles, for example, gearing or toothing, relative to hollow workpieces, the well known Grob method is outstanding. This method will be summarized hereinafter even though in this particular technology or art, both from documentation as well as from actual practice, it is of world renown and no further explanation is needed for those skilled in this art.
For example, the special development of the Grob method, which permits the fabrication of an outer toothing or gearing in a relatively thick-walled hollow workpiece, is disclosed in Swiss Patent No. 579,427, in French Patent No. 75 385 39 and in German Patent No. 25 49 230, to which reference may be readily had and the disclosures of which are incorporated herein by reference. With these methods, different toothings or gear tooth systems can be fabricated on the inside and the outside of the workpiece.
In a relatively thin-walled hollow workpiece, the Grob method permits fabrication, via cold forming or cold working, to simultaneously produce an outer profile and an inner profile, whose profiles may differ. For this, the tubular portion of the raw or unfinished workpiece is mounted on a specific mandrel or holder whose external toothing or teeth correspond to the internal toothing or teeth of the workpiece which is to be fabricated. The workpiece in this setup is infed or advanced along its workpiece axis and turned or rotated relative thereto. During this workpiece feed, the workpiece is externally worked by annular or ring-like profiled forming rolls or rolling tools, whereby each forming roll or rolling tool performs single or individual blow-like or impact-forming operations in rapid succession, in coupled sequence, in the direction of the advance of the workpiece. The single or individual blow-like impact or forming operations are consecutively carried out by the same forming roll or rolling tool in a screw-like or helical zone determined by the infeed of the workpiece. The consecutively following single forming processes, in the direction of the profile, within the same tooth spacing, are accomplished as operations on the workpiece in a partially overlapping manner. In the process of cold forming on the profiled mandrel during each single blow-like or impact forming operation, material is pushed along a relatively small section of the workpiece into the depressions of the mandrel, namely flowing mainly in a radial direction.
With relatively thick-walled workpieces, inner profiles can only be produced via the use of a profiled mandrel. If the form or shape of the outer surface is not of great consequence, it can be finished more or less smooth or even. Rolling heads or forming tools without any profiling may be utilized since they do not have to be exactly synchronized with reference to the rotation of the workpiece.
The production of such hollow workpieces, in the prior state of technical development, substantially dished or pot-shaped hollow workpieces are first produced, as a rule, on very expensive step or transfer presses, in multiple steps. It is only after the last pressing step that the unfinished or hollow bodies can be transferred to Grob machines and mounted on mandrels or holders thereon and be subsequently finished or further worked upon via the Grob method.